Method for drying clay pipe



y 1954 E. c. MILLIKEN METHOD FOR DRYING CLAY PIPE 2 Sheets-Sheet 2 FiledAug. 28. 1951 GAR MOVEMENT Z0 DRYING OVEN AIR MOVEMENT Patented July 6,1954 UNITED STATES ATENT ()FFICE METHOD FOR DRYING CLAY PIPE ApplicationAugust 28, 1951, Serial No. 244,072

1 Claim. 1

This invention relates to a machine for drying clay pipe between themolding and firing operations.

Ordinarily, in manufacturing clay pipe such as sewer pipe, it isnecessary to stand the individual pieces of pipe on end for a period ofsubstantially 48 hours in order to drive the moisture used forplasticizing the clay in the molding operation from the molded pipe to adegree sufficient to permit firing without cracking. In a large sewerpipe factory, the drying of the pipe between the molding and firing is anuisance operation which consumes appreciable floor space and involvessubstantial labor cost. The molding machines must be unloaded and thepipe conveyed from them to the storage space. After 48 hours, the pipeagain must be transported to the mouth of the furnace or kiln in whichit is to be fired, and then loaded into the furnace. Thus, one loadingand one unloading operation are essential for getting the pipe to theplace of storage and a second pair of loading and unloading operationsnecessary for getting the pipe from the place of storage into thefurnace. Furthermore,

a certain percentage of loss results from the drying operation as nowconducted, because the pipe tends to bend or curl toward the side onwhich the air circulation is greater if the air circulation over thepipes being dried is not sufficiently even.

It is the object of this invention to provide a machine for conveyingand drying pipe which eliminates both the conventional prolonged storageand also one of the two loading and unloading operations which are nownecessarily incidental to the prolonged storage.

In its simplest form, which is illustrated in the drawings, the deviceof this invention comprises a two wheel car which carries a plurality ofopen ended perforated pipe drying sleeves or tubes between its wheelswhich are mounted with their inner faces opposing as if upon a singleaxle. While an axle may be used if desired, the function of wheelalignment and attachment may be performed by the sleeves alone. Thefreshly molded clay pipes are loaded into the car, one into each sleeve,at the conclusion of the molding operation. These sleeves are disposedsymmetrically between the wheels in relation to their com mon axis ofrotation so that the car may be easily pushed or pulled and is inbalance in all positions.

The perforated sleeves are slightly larger in diameter than the diameterof the pipes which are inserted in them so that as the two wheel carrotates, each piece of pipe also rotates within its. sleeve.

This car is utilized for conveying the pipe all the way from the outputend of the pipe molder to the input end of the furnace or kiln, and fordrying the pipe en route. At a point intermediate these two stations,the cars are slowly passed through a room, chamber or tunnel which isair conditioned to accelerate the drying out of the pipes. In contrastwith the normal 48 hours drying time, the job can be done successfullyin the much shorter period, such as two hours, provided a flow of air ofproper temperature and relative humidity and velocity is employed, andprovided the exposure of each part of each pipe to the air stream issubstantially uniform. If the exposure is less than substantiallyuniform, then the pipe will tend to curl or bend.

The rotation of each piece of pipe within the sleeve which houses it,not only tends to give each part of each pipe uniform exposure to thedrying air, but also eliminates all tendency of the pipe to sag.Ordinarily, if a freshly molded pipe is permitted to rest in ahorizontal position, as distinguished from being stood on end, then thepipe, still being partially plastic, tends to sag to an oval orelliptical form, as distinguished from a circular form. If, however, thepipe is rotated so that its weight does not rest for too long on any oneaxial line of circumference, then the sagging is not only eliminated,but the pipe tends to be actually rounded to a cylinder by its rollingwithin the sleeve, even if the pipe is less than perfect at the start.

In using the car to convey the pipe from the molder to the furnace, thecar may be advanced steadily and slowly, or intermittently, provided theperiod of rest is not too great at any one time prior to sufficientdrying to reduce plasticity, or the car may be advanced at a speed whichvaries to fit the operating cycle.

The cars of this invention may conveniently pass through a tunnelthrough which the circulation of air may be in any desired direction.However, due to the circumstance that the tubes or sleeves areperforated, it is not essential to pass the air through the pipesaxially. In fact, it is preferred that the air pass through thetunnellongitudinally, with the blast or draft of drying air and carsmoving in opposite or countercurrent directions.

This type of exposure of the pipe to the air blast, that is, a partialexposure of the outer circumference, is the exact type of exposure whichhas been found to produce defective pipe in the ordinary drying roomoperations. It is common knowledge that if there is a draft in a ingroom, such as may be occasioned by an open door or window at one sidethereof, then the pipe which is exposed to this draft tends to curl dueto differential shrinkage between dif ferent arcs of circumference ofthe pipe. Although this type of exposure is used in the pres ent methodor machine, the pipe rotates within its sleeve as the car advances,whereby the entire circumference of the pipe is progressively exposedand no diiierential shrinkage remains as an end result.

More particularly, the pipe, being smaller than the sleeve and restingupon the bottom, presents a limited arc of circumference to the columnof drying air. The air enters the sleeve through the perforations in it,impinges against the pipe, and flows around the circumference of thepipe a distance sufficient to escape through the perforations of thesleeve which are less subjected to the pressure of the air blast.Preferably, the number and size of the perforations are sufficient tobattle the air blast or draft only partially, whereby only a part of theair is deflected sidewise.

Since each piece of pipe rotates within the sleeve which houses it inresponse to forward motion of the car, each piece of pipe rotatescontinuously in the same direction as the wheels of the car, andconsequently, is continuously and progressively supported bycircumferential surface which has been freshly dried by the air blast.

The tunnel should be long enough to accommodate a substantial number ofcars at any one time; the result of which is that any individual pieceof pipe in any individually perforated sleeve, occupies at one time oranother every possible position in relation to the stream of drying air,whereby each piece of pipe is subjected to the same amount of drying aseach other piece of pipe, and the engagement of the stream of drying airwith the outer surface of each individual piece or" pipe dries all 360of the pipe wall uniformly. In order to insure this effect, the tunnelshould be sufliciently long to permit several revolutions of each carwithin the tunnel.

In a tunnel of any length, it is diificult, if not impossible, tomaintain uniform temperature between the top half of the tunnel and thebottom half of the tunnel. However, in the practice of the presentinvention, such unevenness of temperature as cannot be controlled is nodisadvantage, because each piece of pipe, rotating as it does about theaxis of revolution of the wheels of the car, is being dried at acontinuously changing eleva ion, so that each piece or" pipe isinherently exposed successively to different temperature and draftconditions within the tunnel, whereby drying conditions and exposuresare averaged and it is unnecessary to overdry some individual pieces ofpipe in order to insure sufiicient drying for other individual pieces ofpipe. Various air blasts or air conditioned chambers may be used insteadof the tunnel, but the use of the tunnel is the simplest way ofobtaining the requisite drying in the shortest period of time.

Quite obviously, the exact layout of this system of conveying and dryingpipe depends upon the architecture, design and dimensions of the plantin which the system is installed. C-rdinarily, the pipe molder and thefurnace are some distance apart or even in separate buildings because ofthe necessity for substantial drying acreage in between them. Dependingupon the conditions of the plant where the system is installed, thewheels of each car may be provided with tires which are suitable for thesystem. For instance, the car wheels may be provided with pneumatictires and pushed by hand or provided with stub axles and propelled by anendless belt or chain which is axle high, or both. If rapid rotation isdesired, small wheels may be put on the axle stubs and the cars advancedalong an elevated track. For most purposes, however, it is believed tobe better to use a track which rests directly upon the ground and toprovide the wheels the car with flanged metal tires so that the car runsbetween the track. The tires and wheels may, of course, be integral, andsince the cars do not move at any substantial rate of speed, the flangesmay be of sufficient width to maintain the alignment of wheels on thetrack without undue binding or friction.

The track may provide a complete circuit whereby the car passes from theunloading station of the molder to the drying tunnel, to the loadingstation of the furnace, then back to the molder. The cars may be pushedby hand or by mechanical means, or may be permitted to roll slowly bygravity. For any installation of the system, specific features must beincorporated to adapt the system to the needs of the particular plant.Whenever desired, the drier cars may be joined together to operate intandem by means of removable bars which may be attached to the ends ofthe stub axles of any two or more cars.

In the accompanying drawings:

Figure 1 is a side elevation of the car of this invention.

Figure 2 is an end elevation.

Figure 3 is a sectional View taken on line 3-3 of Figure 1.

Figure 4 is a diagrammatic View illustrating a typical plantarrangement.

Figure 5 is a diagrammatic side elevational view showing a modifiedtrack arrangement.

Figure 6 is a diagrammatic side elevational view showing three carslinked together in tandem.

Figure 7 is a cross sectional view taken on line 7-? of Figure 6.

From the point of view of method, the pipe manufactured by means of thisinvention is an improvement over pipe manufactured by ordinary methodsin two respects. The first is that, as an incident to conveyance betweenthe molder and the furnace, the pipe is rolled on its circumference toinsure a truely circular cross section. This is accomplished by movingthe axis of the individual piece of pipe on a path which is cycloidalwhile at the same time rotating the pipe on its axis. In the secondplace, the subjection of the pipe to a countercurrent blast or draft ofdrying air, while being rotated and moved upon the cycloidal pathindicated, results in evenness oi" the drying which insures themaintenance of circular cross section.

More particularly, each car comprises two wheels ill-l0 which areconnected together by tubes or sleeves ll perforated as at i2. In Figure2 of the drawings, only one of the sleeves is shown as being perforated,however, it will be understood that all the sleeves in a car arepierced. Each wheel, in the present instance, is made from a circularwall or web ill of sheet metal which has a plurality of round holes cutin it to accommodate the perforated sleeves. Preferably, the sleeves arewelded circumferentially to the web as shown at M in Figures 3 and 7.The outer edge of each web is turned over to provide a peripheral flangewhich seats a metal tire 16. The tires may be made from angle ironmaterial formed in a circle. This construction provides a radial flangeIT at the inner edge of each tire, whereby the car may be moved along atrack of metal, masonry, wood or any other desired material.

The sleeves themselves are symmetrically disposed in relation to theaxis of rotation of the wheels, whereby the unit is at all times inbalance. In addition, the sleeves may have flared ends 18 to facilitateloading. In order to insure a true circular cross section for the pipe,the sleeves are slightly larger in diameter than the pipe so that thepieces of pipe roll in the sleeves as the car rolls, this relationshipbeing shown in Figures 1 and 8.

Although the drawings illustrate the simplest construction, it will beunderstood that the structure may be further rigidified by an axleextending between the wheels or may be supplemented by stub axlesextending to the outside of each wheel, or both. In any event, thewheels joined by the tubes are positioned in relation to each other asif upon opposite ends of an ordinary axle.

In Figure 4, which shows schematically a typical plant arrangement, atrack 20 extends from the delivery end of a pipe moulding station 2| toa tunnel drying oven 22 through which it passes. Air may be blownthrough the tunnel by means of a conventional blower, not shown, in thedirection counter to the indicated car movement. It is to be understoodthat the air sup-,

plied by the blower may be heated or dehydrated to whatever extent localconditions may require. If desired, the track may be arranged in theform of a closed circuit extending from the tunnel 22 to the deliveryend of a furnace (not shown), and from there, back to the delivery endof the pipe molding station 2|.

No mechanism for advancing the cars is disclosed for the reason that anydesired combination of operations performed by manual labor and bymechanical implements may be employed. If desired, the track may begently sloped all the way from the molder to the furnace, and the motionof the cars retarded intermittently by means of blocks manually appliedto the tracks. The cars may be pushed up the incline from the furnace tothe molder manually. Alternatively, as much automatic equipment asdesired may be utilized to implement or displace the manual labor.

In order to provide an increased rate of rotation for the pipes in thecars, an elevated track such as the one shown at 23 in Figure 5 may beemployed, this track accommodating small diameter car wheels 24 whichare mounted upon stub axles. Thus, in the instance shown, the cars rollon the tires I6 from the pipe molding station to a point near the dryingoven where car wheels 24 engage the elevated track 23. It will beappreciated that elevated tracks may be utilized throughout the circuitor in any portion of the circuit where greater rotative speed than thatprovided by rolling the cars upon tires I6 is desired.

Figures 6 and '7 illustrate a modification in which the cars are linkedtogether in a train by means of bars such as those shown at 25. Thesebars may have slots 26 at their respective ends which engage over stubaxles 2|2I extending outwardly from the respective sides of the wheelsupon their axis of rotation. Spaced collars 28-28 may be used forseating the slotted ends of bars 25 as illustrated in Figure 7.

By means of these cars and this system, the problem of (/Jnveying pipefrom the molder to the furnace is substantially simplified and theprolonged drying of the pipe without all of the attentant spaceconsumption and pipe handling complications is eliminated. Additionally,the quality of the pipe which is rolled during drying in the perforatedsleeve is more uniform and better than pipe which has been dried byprolonged standing on end.

Having described my invention, I claim: The method of conveying freshlymolded plastic clay pipe from the molder to the furnace in 1 which thepipe is to be fired and drying the pipe sufficiently en route to permitfiring, said method comprising supporting the freshly molded pipe in ahorizontal position by means of a circumferential support which has adiameter slightly exceeding that of the pipe, rolling the pipe in thecircumferential support by advancing the circumferential support in acycloidal path from the molder to the furnace, and blowing a stream ofdrying air in a direction countercurrent to said cycloidal path over adistance greater than one cycle of said path.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,458,393 Chapman June 12, 1923 1,498,774 Baldwin June 24,1924 1,822,158 Majer Sept. 8, 1931 1,933,051 Fanta Oct. 31, 19332,039,129 Vance et al. Apr. 28, 1936' 2,219,166 Schaefer Oct. 22, 19402,554,705 Jewell May 29, 1951 2,618,075 Everhart Nov. 18, 1952

